Also if you join the College of Winterhold, five bowls Ectoplasm can be taken in the Hall of Countenance. You can also steal two samples inside the Archmage’s Quarters. Alternatively, you can check alchemy merchants for Ectoplasms. It’s considered as an uncommon ingredient, but merchants have a 15% chance of carrying about 1-5 samples of Ectoplasm. Never hurts to check!
Rannveig’s Fast
You can find this Nordic ruin northeast of Rorikstead. Before entering the ruin, you’ll encounter several subjugated ghosts and a ghost adventurer – both of which drop Ectoplasm when killed. So try to take them out before moving further. Inside the ruin you should notice up to 5 subjugated ghosts patrolling its halls. They aren’t particularly strong opponents and are poorly armed, so farming ectoplasm here should be very simple.
Yngvild
Northeast of Dawnstar you’ll find Yngvild, which is inhabited by Draugrs and Yngvild Ghosts. The first area has four Yngvild Ghosts and several Draugrs you can fight for drops. The next area nearby is called the Yngvild Throne Room. Inside there you should find 3 ghosts you can try for drops, and 2 samples of Ectoplasm on a table near the throne. Note that mage sitting at the throne is hostile and will attack you on sight.
Abandoned Prison
This place can be found near a waterfall southwest of Mixwater Mill in Eastmarch. Get into the area and once you reach the end of the prison, you’ll find prison cells. Two ghosts can be found here. Another ghost is locked behind a cell door with an expert-difficulty lock. This may not be worth farming but it’s really up to you.
Ectoplasm Uses in Skyrim
Ectoplasms have Restore Magicka, Fortify Destruction, Fortify Magicka and Damage Health effects.
You can combine Ectoplasms with Mora Tapinella or Jazbay Grapes to create a Fortify Magicka Potion.
And if you combine some Ectoplasm with some Nightshade (or a handful of other ingredients) you can create a Potion of Fortify Destruction which enhances Destruction spells and increases maximum magicka.